/*
 * Copyright 2010 The Apache Software Foundation
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.hadoop.hbase.filter;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.util.ArrayList;

import org.apache.hadoop.hbase.KeyValue;

import org.apache.hadoop.hbase.util.Preconditions;

/**
 * A filter, based on the ColumnCountGetFilter, takes two arguments: limit and offset.
 * This filter can be used for row-based indexing, where references to other tables are stored across many columns,
 * in order to efficient lookups and paginated results for end users.
 */
public class ColumnPaginationFilter extends FilterBase {
	private int limit = 0;
	private int offset = 0;
	private int count = 0;

	/**
	 * Used during serialization. Do not use.
	 */
	public ColumnPaginationFilter() {
		super();
	}

	public ColumnPaginationFilter(final int limit, final int offset) {
		Preconditions.checkArgument(limit >= 0, "limit must be positive %s", limit);
		Preconditions.checkArgument(offset >= 0, "offset must be positive %s", offset);
		this.limit = limit;
		this.offset = offset;
	}

	/**
	 * @return limit
	 */
	public int getLimit() {
		return limit;
	}

	/**
	 * @return offset
	 */
	public int getOffset() {
		return offset;
	}

	@Override
	public ReturnCode filterKeyValue(KeyValue v) {
		if (count >= offset + limit) {
			return ReturnCode.NEXT_ROW;
		}

		ReturnCode code = count < offset ? ReturnCode.SKIP : ReturnCode.INCLUDE;
		count++;
		return code;
	}

	@Override
	public void reset() {
		this.count = 0;
	}

	public static Filter createFilterFromArguments(ArrayList<byte[]> filterArguments) {
		Preconditions.checkArgument(filterArguments.size() == 2, "Expected 2 but got: %s", filterArguments.size());
		int limit = ParseFilter.convertByteArrayToInt(filterArguments.get(0));
		int offset = ParseFilter.convertByteArrayToInt(filterArguments.get(1));
		return new ColumnPaginationFilter(limit, offset);
	}

	public void readFields(DataInput in) throws IOException {
		this.limit = in.readInt();
		this.offset = in.readInt();
	}

	public void write(DataOutput out) throws IOException {
		out.writeInt(this.limit);
		out.writeInt(this.offset);
	}

	@Override
	public String toString() {
		return String.format("%s (%d, %d)", this.getClass().getSimpleName(), this.limit, this.offset);
	}
}
